The present invention relates to improvements to a pointing device, such as that disclosed in commonly assigned U.S. Pat. No. 5,045,843, the entirety of which is herein incorporated by reference.
The invention which is the subject of U.S. Pat. No. 5,045,843 satisfies a need for a system facilitating remote control of a cursor on a display screen. FIG. 1 illustrates an example of a basic block diagram of the pointing device, shown at 40, according to the prior patent. A first unit 41, called a fixed unit or base unit, is located proximate the display screen and interconnects with a cursor control circuit 13 associated with the display screen 15, such as a television or a computer display screen.
The fixed unit 41 includes a driver 7 and a first LED 9. A microcomputer 5 controls operation of the driver 7 as well as operation of the cursor control circuit 13. The fixed unit further includes a photodetector 43 connected to the microcomputer 5 via an analog-to-digital converter 16 and a buffer 45.
The movable or remote unit 48 includes a camera 19 having a lens 21, an elongated tube 23 and a position sensing detector 25 connected to operational amplifiers 29. The operational amplifiers 29 amplify the currents received and translate them into proportional voltages. The voltages are digitized by the A/D converter 49 and processed by the microcomputer 51 to control operation of the driver 55 which drives a second LED 57.
In order to compensate for ambient light conditions, the system according to the prior patent performs active dynamic gain control in the fixed unit by two-way ("closed-loop") communication between the fixed unit and the moveable unit. Specifically, the intensity of the light transmitted by the LED of the fixed unit is controlled. This light intensity is proportional to the square of the distance between the fixed unit and the moveable unit. The fixed unit and moveable unit communicate with each other in both directions to establish appropriate illumination levels of the IR LED 9 in the fixed unit. The amplified output signals of the operational amplifiers are then digitized by the A/D converter 49 to allow for processing by the microcomputer 51. The step of digitizing the amplified signal for ultimate transmission is hereinafter referred to as "information reporting".
While the system according to the prior patent adequately performs its desired functions, there is room for improvement. Specifically, it is desirable to eliminate the need for two-way, or closed-loop, communication and to accomplish automatic gain control by adjusting the gain of the operational amplifiers in the moveable unit. It is also desirable to eliminate the A/D conversion in the moveable unit.